Bursty Bulk Flows(BBF) events are an important phenomenon of plasma transport in the Earth’s magneto tail during substorms, and can be explained by the bubbles model. Although the theories and observations have provided some estimates of the important parameters of BBFs, such as the cross tail size, these parameters are still an extent instead of accurate value. Based on the latest Tsyganenko magnetospheric model, we provide the cross tail size of BBFs in the magnetic equatorial plane through the north south aligned auroral structures and tracer program. The results show that the predications of the bubbles model agree with the observed facts.
